When the head of the tibia is fractured, a load-bearing fracture surface must be reconstructed. The tibia is the only bone in the body where there is a continuous transition from a cubic bone with a load-bearing articular face into a tubular bone. In the area of the head of the tibia, load forces acting axially on the proximal articular tibia surfaces are converted continuously into a load on the tubular bone. No specific implants for these conditions have been available so far. An ideal load-bearing device for the head of the tibia must take these specific conditions into account.
In the related art various straight plates and angle plates as well as intramedullary nails are available for treating fractures of the head of the tibia. However, all these implants are designed for strong young bones and so far have been used mainly to treat accident-related fractures (sports and athletic accidents, labor accidents and traffic accidents).
However, due to aging of the general population and also the level of activity being pursued by the elderly population, the medical profession is increasingly confronted with the need for treating fractures in osteoporotic bones.
Osteoporosis is a growing problem in health care. The percentage of patients over 80 years of age has increased drastically, so there has also been a definite increase in fractures in patients with osteoporosis. Fractures of the proximal and distal tibia, the proximal and distal femur as well as the proximal humerus and the distal ulna and radius are of primary concern.
Previous osteosynthetic implants according to the related art are not very suitable for use with osteoporotic bones where the cortex is thin and spongy tissue is of an inferior quality. It is often difficult to correctly reposition fragments when the cortex is thin. Fixation and/or immobilization of a repositioned fracture is often extremely problematical in osteoporotic bones because osseous anchoring of the implants is difficult.
Regardless of bone quality, implants that arc truly optimized for treatment of proximal tibia fractures and in particular fractures of the head of the tibia have not been available. Only a few slightly modified plates and intramedullary nails are available.
European Patent No. 118,778 describes a locking nail with an elongated hollow body which is rounded at the proximal end and has an end with a widened head. In addition, at least two cross bores are provided in the body to accommodate one bone screw in each. The cross-sectional profile of the body forms a closed ring over its circumference.
Another locking nail made of solid material is disclosed in European Patent No. 447,824 FRIGG, where the proximal end part has a cross-sectional area with a trigonal shape in both the anterior and the posterior halves while being approximately quadratic as a whole. The distal end part has a cross-sectional area which is approximately trigonal in the anterior half and is approximately hemispherical in the posterior half. This specific design of the intramedullary nail according to this invention causes a high rotational stability in the proximal spongy part of the tibia while on the other hand permitting the most optimal possible adaptation to the geometry of the medullary space in the distal confocal part of the tibia.
Another locking nail is known from German Patent No. 43 41 677 SCHROEDER The nail body is rounded at the distal end and has a proximal concave end. Cross bores to accommodate one bone screw each are arranged in the nail body. In addition, the nail body is made of a solid material and has a funnel-shaped opening at least on one side of each cross bore.